30 SEAWEEDS 
alcohol, to remove as much air as possible. It should 
then be transferred to salt and water, and permitted 
to remain in it. A drop or two of glycerine should 
be added, and the process may be hastened by gently 
heating, not boiling. The most successful specimens 
are those that have been kept at about 90° F. for 
several hours. Material so treated may then be 
preserved in spirit (at first weak, and gradually 
strengthened). 
Living specimens to be preserved in spirit should 
be first treated with picric acid. A saturated solu- 
tion of picric acid in sea-water should be made and 
subsequently diluted with three or four times its 
volume of sea-water. The specimens should be im- 
mersed in it from a quarter of an hour to two hours, 
according to size and density; then washed in 
sea-water and placed first into weak spirit, and by 
degrees into stronger spirit. Specimens vary greatly 
as to the result of treatment by picric acid. To ob- 
tain thorough fixation of the contents of such Alge 
as Valonia (Fig. 46) it is necessary to immerse them 
for several hours in the saturated solution itself. 
For mounting microscope slides of seaweeds the 
best medium is clear glycerine jelly, which has the 
advantage of being easily manipulated. The examin- 
ation of Algze encrusted with carbonate of lime, such 
as the stony corallines, is facilitated by the use of 
Perenyi’s decalcifying fluid (4 vols. 10 per cent. nitric 
acid, 3 vols. absolute alcohol, and 3 vols. 5 per cent. 
chromic acid), which gives better results than weak 
hydrochloric acid or any other method in common 
use. It is particularly valuable in examining Algze 
